validate_phone

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations provided, so description bears full burden. It discloses normalization to E.164 and returns valid:false for invalid numbers, but does not explicitly describe the return structure for valid numbers (e.g., whether it returns the normalized number or a full object). Lacks some completeness.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with immediate clarity: first sentence defines purpose, second gives usage and return info. No unnecessary words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple validation tool with no output schema, the description covers essential aspects: purpose, usage, parameters, and basic behavior. Slightly incomplete on return value details but generally adequate.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description adds meaning by specifying that 'number' is the raw input and 'region' should be 'GB' or 'US' with default 'GB'. Adds useful context beyond the schema alone.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool validates and normalizes phone numbers to E.164 format, with an example. It effectively distinguishes from siblings by being the only phone validation tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly advises using this tool before saving, dialling, or sending SMS, and instructs to pass region 'GB' or 'US'. Provides strong usage guidance without ambiguity.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.